[TargetLowering] Use ISD::FSHR in expandFixedPointMul
Replace OR(SHL,SRL) pattern with ISD::FSHR (legalization expands this later if necessary) - this helps with the scale == 0 'undefined' drop-through case that was discussed on D55720.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353546 91177308-0d34-0410-b5e6-96231b3b80d8